A strong upper ridge built slowly inland into California between May 12 and May 14 which brought a significant warming trend to the area with temperatures rising to well above normal levels by May 13 after colder than normal temperatures prevailed for the first 11 days of the month. Portions of the southern San Joaquin Valley had high temperatures above 100 degrees F on May 14 which was the…
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The episode as NWS HNX wrote it up.
A strong upper ridge built slowly inland into California between May 12 and May 14 which brought a significant warming trend to the area with temperatures rising to well above normal levels by May 13 after colder than normal temperatures prevailed for the first 11 days of the month. Portions of the southern San Joaquin Valley had high temperatures above 100 degrees F on May 14 which was the first day of triple digit heat in several months which resulted in elevated heat related impacts. Temperatures cooled a little by May 15 as the ridge weakened slightly.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Hanford, CA wrote its last area forecast discussion before the first event at May 14, 2:05 AM PST, 7 hours 55 minutes earlier.
Area Forecast Discussion National Weather Service Hanford CA 305 AM PDT Sun May 14 2023 .SYNOPSIS... Much above average temperatures will prevail across the area through next week. The Sierra Nevada may also see a few thunderstorms in the afternoons on Sunday and again by late next week. && .DISCUSSION... Main concern this morning will be the development of convective showers across the Sierra Nevada and the continuation of heat across Central California. Satellite imagery this morning is showing mostly clear skies across Central California with circulating clouds over the Great Basin. Radar and upper-air analysis is currently showing the center of circulation over East Central NV. Upper-air analysis is also showing the Low over NV as being part of a Blocking High pattern over the West Coast. With that, heat will affect much of the Central California Interior this weekend and into the start of the work week (Monday). A Heat Advisory is currently in-effect for the San Joaquin Valley as we are on our way to reaching the mid-90s this Sunday afternoon. Ensemble model analysis is showing minimal error in the short- term with the development of the upper Low over East-Central Nevada. This minimal error gives the ensemble solution higher confidence toward the low retrograding in the direction of Yosemite NP this afternoon. Therefore, will expect a 15 to 25 percent chance that Yosemite will see Thunderstorm activity. South of Yosemite, the percentage of possible convective activity drops below 15 percent and is closer to 10 percent this afternoon from Fresno to Tulare Counties. Convective clouds will start after 1100 PDT with Thunderstorm activity beginning between 1300 and 1500 PDT. With convective indices showing values that will keep the thunderstorm on the weak side, the chance of reaching severe weather magnitude is less then 10 percent today. Ensemble upper- air analysis showing the upper Low moving into Oregon overnight into early Monday as Central California losses the weak instability that will be seen this Sunday. Blocking pattern then dominates the region for a continuation of warm temperatures for much of the week. Temperatures-wise, NBM surface point analysis shows valley max temperatures having Probability of Exceedance (PoE) of reaching and passing 95 degrees in the 40 to 60 percent range for Sunday. Therefore, with Kings and Kern Counties showing the higher PoE percentages, will expect those counties to see higher temperature values today. Probability of Exceedance of reaching 95 degrees grows to 60 to 80 percent on Monday. Therefore, will expect areas south of Merced County to reaching the mid to upper 90s on Monday. Merced County’s PoE goes above 60 percent on Tuesday which could provide the north end of the district with max temperatures in the mid 90s. This trend toward warmer temperatures will lead to increased snow-melt runoff and increase the flow of Central California’s rivers and creeks. Flood products are currently in- effect as our rivers remain dangerous. Long-range Cluster analysis shows minimal change away from the current ridge pattern. Therefore, warm temperature will persist throughout the week and into next weekend. && .AVIATION... Will expect a 15 to 25 percent chance that Yosemite/Madera County Mountains will see Thunderstorm activity beginning between 20Z and 22Z today and ending after 02Z to 04Z Monday. Otherwise, VFR conditions will prevail throughout the Central CA interior for the next 24 hours. && .AIR QUALITY ISSUES... None. && .CERTAINTY... The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information and/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM PDT Monday for CAZ301>307-309>312- 314>316. && Public/Fire Wx/IDSS..........Molina PIO/Social Media/Aviation....EW weather.gov/hanford
The national radar mosaic for the moment the first event began.
5 heat. Local standard time, as filed.
Daytime highs ranged between 99 and 102 degrees on May 14.
Daytime highs ranged between 99 and 102 degrees on May 14.
Daytime highs ranged between 99 and 102 degrees on May 14.
Daytime highs ranged between 99 and 102 degrees on May 14.
Daytime highs ranged between 99 and 102 degrees on May 14.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2023Every state in 2023This day in weather historyWarnings in California, May 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1088196, 1088197, 1088198, 1088199, 1088200.